The invention concerns a fifth wheel coupling for the articulated connection of a tractor to a semitrailer, with a fifth wheel coupling plate secured by bearing elements on the tractor, having a cutout with a central recess and a lock for accommodation of a kingpin permanently mounted on the semitrailer at the center of an upper plate, and which has a friction-reducing sliding layer.
Fifth wheel couplings are used for form-fitting, yet articulated connection of a tractor to a semitrailer, which then together form a so-called double train. The fifth wheel coupling has a fifth wheel plate with a typically V-shaped or mouthlike insertion cutout, also known as the coupling or capture mouth, which is bounded on both sides by a somewhat downward sloping horn. The V-shaped notch is typical, but not necessary. There can also be a coupling from above in the cutout. The insert cutout, the coupling mouth, passes into a central recess, in which a wearing ring is typically but not necessarily placed. On either side of the wearing ring, if present, there are lock elements, especially a locking hook, which are disengaged from the central recess when the fifth wheel coupling is open. The coupling plate can swivel and is joined to the frame of the tractor primarily by means of bearing blocks and possibly a mounting plate.
On the semitrailer, at the bottom of the front end, there is an upper plate on which is arranged a downwardly pointing coupling or kingpin. In the coupling process, this pin is guided by the coupling mouth in the coupling plate and inserted into its central recess until it comes to lie against the wearing ring. The upper plate forms, as it were, the counterplate to the coupling plate. As soon as the kingpin lies against the wearing ring, the lock elements are brought into the locking position, whereupon the locking hook embraces the kingpin with form fit, yet able to rotate.
Fifth wheel couplings of the above kind are generally known and are largely standard equipment on double trains (DIN74080=ISO 337).
Fifth wheel couplings of the above kind must satisfy several requirements. The weight of the semitrailer, the supporting or surface load, as well as all tensile and compressive forces occurring during turns and uphill travel, which are introduced via the kingpin, must be transmitted to the frame of the tractor. Coupling plates which according to the state of art were heretofore exclusively single-piece design (for example, see DE 296 03 641 U1) therefore have to be massively constructed in order to absorb the aforesaid forces. As a consequence, a relatively large amount of material is required for the production of the coupling plate and this is therefore correspondingly heavy.
Another fundamental problem with such couplings is the friction between the coupling plate and the upper plate on the semitrailer, especially because of the constant relative motions between them while traveling on curves.
In order to deal with this problem, it is known (DE 35 30 467 A1; EP 0 117 319 B1; DE 44 18 533 C2) how to provide a coating or fastening of antifriction materials on the coupling plate. Usually these antifriction materials have the form of arc-shaped sliding coatings which preferably consist of plastic and which are embedded in corresponding recesses in the metallic coupling plate and secured there, for example, by gluing or preferably by screwing, so that the sliding layer projects somewhat above the metallic coupling plate. The sliding layer can be bent like a horseshoe or have two approximately semicircular sliding layers, as in the case of the aforesaid DE 296 03 641 U1, which are screwed together with the coupling plate.
The basic goal of the invention is to configure the above-mentioned fifth wheel coupling such that, while reducing the material outlay, its weight is considerably decreased and a modular construction is possible.
The solution of this problem, according to the invention, is that the coupling plate consists of two mechanically connectable, separate structural components, with an upper bearing component, which interacts with the upper plate, and with a lower carrying component, in which the central cavity with the lock is placed.
The lower beamlike carrying component is basically assigned the function of transmitting the force from the kingpin to the bearing and, thus, to the frame of the tractor. It accommodates the locking mechanism with the wearing ring, if present.
In the fifth wheel coupling according to the invention, therefore, only the lower beamlike carrying component absorbs the support load and the large forces introduced by the kingpin, namely, the tensile forces when traveling on level and rising terrain, the compressive forces on falling terrain, as well as the transverse and lift forces when traveling on curves, so that only this carrying component needs to be mechanically stable in configuration, and a considerable savings in material can be achieved thanks to the beamlike construction. The upper plate-like bearing component need only be designed for the surface load of the semitrailer, also known as the vertical load, since its only task is to bundle the forces originating in the upper plate of the semitrailer and to transfer them to the carrying component, and therefore certain degrees of freedom in design result in terms of the shape of this component and the materials used for its production.
Another task of the bearing component is to provide low frictional moments when traveling on curves.
Since the upper bearing component is exposed to the greatest wear, besides the friction in the wearing ring (if present), now that it is free from the function of absorbing the considerable forces produced by the kingpin it can be designed, in particular by choice of appropriate materials, specifically for the requirements of:
low maintenance
corrosion protection
low weight.
The breaking up of the functions of a fifth wheel coupling between the two components also enables a modular design with great benefit.
One can keep in stock lower beam carrying components designed for different load uptake in the manner of a prefabricated unit and combine them in easy and economical fashion with upper bearing components of various design.
According to a first embodiment of the invention, the bearing component is screwed together with the carrying component. This embodiment allows a simple construction.
Several structural options are available to the practitioner for the connection of the two components. Preferably, because it allows a good and easy to produce fastening, the connection of the two components is by means of screws. For this, according to another embodiment of the invention, a circular ring-shaped molding with several fastening holes is provided on the lower beamlike carrying component, and a congruent crown of fastening holes is provided on the upper bearing component to receive fastening screws.
By separating the functions, one obtains degrees of freedom in the configuration of the upper bearing component. Thus, according to one embodiment of the invention, it is possible to make them out of metal, preferably steel, or aluminum or cast iron. Connection elements can be provided on it for a preferably form-fitting connection to sliding linings forming a sliding layer.
One alternative to this is to coat the entire upper bearing component with a sliding layer, consisting preferably of a plastic which has good sliding properties, like teflon, and which forms a corrosion protection for the steel plate.
According to another embodiment of the invention, the upper bearing component can consist entirely of plastic. The plastic is preferably a fiberglass-reinforced plastic and/or has a reinforcement in the form of embedded pieces. It can also be a multilayered body, with a lower carrying layer and an upper sliding layer.
There are also several possible configurations for the horns bordering the typically V-shaped notch. Thus, these horns can be formed either on the upper bearing component, which then has a conventional shape, or the horns are placed on the lower carrying component, in which case the upper bearing component can then have the simple shape of a circular ring with a V-cutout. The horns can be molded as a single piece with the corresponding component; however, to foster a modular design, it is advisable for each horn to be a separate piece, which can be detachably connected to the corresponding component. Therefore, when wear occurs, only the corresponding horn and not the entire component need be replaced.
There are also several options available to the practitioner for the configuration of the lower beamlike carrying component. According to a further embodiment of the invention, this carrying component consists of three beams, a main middle beam as well as secondary side beams each parallel with it, which are joined together at both ends to form the base for the bearing element at the coupling side. According to a further embodiment of the invention, the bearing element can be molded as a single piece with the base; however, it is preferable for the bearing element to be a separate component, which can be detachably connected to the base. This technique also supports the benefits of the modular design.
There are also several options for the practitioner in mounting the lower carrying component on the double train. According to a preferred embodiment, the bearing element is a journal, and the corresponding split bearing is formed immediately in the frame of the double train, and a clamplike component embracing the journal at the top and secured to the frame is provided to attach the journal.
Additional benefits, especially as regards the design of the components and a modular construction, will result if, according to a further embodiment of the invention, the bearing component consists of two separate platelike parts, known as wing plates, which are arranged on either side of a platelike middle piece provided at the center of the carrying component, which has the V-cutout with horns bounding it, preferably detachable.
There are various design solutions for the mounting of such a divided coupling plate in the bearing elements 5 on the double train. A first solution consists in that the two wing plates are secured on the beamlike carrying component, preferably being screwed to it, and the carrying component is accommodated in the bearing elements on the double train.
As compared to the above-described notion with an undivided bearing component, the advantage is that the forces act closer to the beam end of the carrying component, i.e., it is not exposed so heavily to bending stress.
A second solution is that the carrying component has two carrying beams, on which the two wing plates are held and can move, each of them being accommodated in one of the bearing elements on the double train.
In this solution, the wing plates advantageously divert the support load directly into the bearing sites, i.e., the forces are diverted directly into the frame of the double train. Moreover, thanks to the movability of the wing plates, different frame widths can be covered with the same component.
A third solution consists in that the beamlike carrying component has a journal at each of the beam ends, which is accommodated in one of the bearing elements on the double train and secured to a wing plate.
In this solution as well, the wing plates directly conduct the vertical load into the bearing sites, i.e., the frame.
Further configurations and advantages of the invention will result by means of the description of the sample embodiments of the invention as depicted in the drawings.